Populations of spleen cells enriched for antigen specific cells from virgin and immune animals will be prepared. Particular attention will be given to determining the conditions in which virgin cells can be prepared without activating them by the techniques used for enrichment. These procedures will probably involve the use of various types of inhibitors. The cell surface events that accompany interaction of antigen specific cells with tolerogen and immunogen will then be correlated with functional in vitro analysis of the results of such interaction. The epitope density of the tolerogen or immunogen will be an important variable in such studies. Using anti-micron and anti-delta specific antiserum, attempts will be made to correlate the behavior of particular isotype receptors with the resultant immune responses.